Seismic anisotropy of upper mantle in eastern China |
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Authors: | LiJun Chang ChunYong Wang ZhiFeng Ding |
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Institution: | (1) Institute of Geophysics, China Earthquake Administration, Beijing, 100081, China |
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Abstract: | Based on the polarization analysis of teleseismic SKS waveform data recorded at 65 seismic stations which respectively involved
in the permanent and temporary broadband seismograph networks deployed in eastern China, the SKS fast-wave direction and the
delay time between the fast and slow shear waves at each station were determined by use of SC method and the stacking analysis
method, and then the image of upper mantle anisotropy in eastern China was acquired. In the study region, from south to north,
the fast-wave polarization directions are basically EW in South China, gradually clockwise rotate to NWW-SEE in North China,
then to NW-SE in Northeast China. The delay time falls into the interval 0.41 s, 1.52 s]. Anisotropic characteristics in
eastern China indicate that the upper mantle anisotropy is possibly caused by both the collision between the Indian and Eurasian
Plates and the subduction from the Pacific and Philippine Sea Plates to the Eurasian Plate. The collision between two plates
made the crust of western China thickening and uplifting and the material eastwards extruding, and then caused the upper mantle
flow eastwards and southeastwards. The subduction of Pacific Plate and Philippine Sea Plate has resulted in the lithosphere
and the asthenosphere deformation in eastern China, and made the alignment of upper mantle peridotite lattice parallel to
the deformation direction. The fast-wave polarization direction is consistent with the direction of lithosphere extension
and the GPS velocity direction, implying that the crust-upper mantle deformation is possibly a vertically coherent deformation.
Supported by Special Project for the Fundamental R & D of Institute of Geophysics, China Earthquake Administration (Grant
No. DQJB06B06), Special Program of the Ministry of Science and Technology of China (Grant No. 2006FY110100), China Digital
Earthquake Observation Network Project “North China Seismic Array”, and National Natural Science Foundation of China (Grant
Nos. 40334041 and 40774037) |
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Keywords: | eastern China upper mantle anisotropy SKS wave fast-wave direction lithosphere deformation |
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